Get reliable science

Psidium guajava (guava) is recognised as the third most important invasive alien plant species in the
moist savanna biome of South Africa, Lesotho and Swaziland. The cost of initial clearing of alien plants
reaches up to R3 000-00 per ha, therefore the application of correct control methods is essential for
cost-effective reduction of the spread. The aim of this study was to test the cost effectiveness of
applying various herbicides to guava in the Swaziland Sour Bushveld. Four plots were selected for
standing plant treatments, five for cut stump treatments and two for controls. Within each of these
plots, five sub-plots were randomly located and the number of plant stems, base diameter, maximum
height, and crown diameter was recorded before application of the herbicides. Picloram, fluroxypyr,
bromacil, tebuthiuron and imazapyr were used either alone or in combinations. Eleven months after
herbicide application, the treated plants were measured again. Bromacil/tebuthiuron liquid soil
application gave the best results in terms of cost (0.09 c/stem) for standing plant treatments. The
picloram/fluroxypyr cut stump treatment (4.5% concentration) cost the least to apply (0.05 c/stem), and
no resprouting was observed. Results from this study can be used as baseline figures for managers
planning to control guava.